1. Field of the Invention
The present invention concerns turbine generator units particularly but not exclusively intended for the production of electricity in thermal or nuclear power stations, especially in locations subject to subsidence, and it is more particularly concerned with the installation of the turbines and condensers which such units comprise.
2. Description of the Prior Art
Turbine generator units of this kind comprise an elevated part or table to which is fixed the body of the low-pressure turbine. This table is supported by columns resting on a foundation slab, the condenser being supported beneath the turbine and coupled to it by a connecting sleeve.
There exist a number of turbine generator unit installations which differ from one another in terms of how the condenser is coupled to the turbine, to the table and to the foundation slab.
In the so-called "suspended condenser" arrangement, the condenser is mounted on springs and coupled to the turbine by a rigid connecting sleeve welded to their respective outer jackets. This arrangement, which is the conventional one in Europe, protects the table from the effect of atmospheric pressure when the condenser is evacuated. However, it has the disadvantage of transmitting to the turbine body unwanted loads resulting from variations in the quantity of water in the condenser and variations in the spring reaction forces associated with expansion of the condenser body.
A second so-called "seated condenser" arrangement consists in placing the condenser on the foundation slab and providing an airtight flexible joint in the connecting sleeve welded to the turbine and to the condenser. The latter is thus mechanically decoupled from the turbine, which is then not affected by thermal expansion of and variations in the quantity of water in the condenser. However, it is then the foundation slab which has to withstand the full atmospheric pressure loading when the condenser is evacuated, and this loading is typically substantially the same as the total weight of the turbine generator unit.
The tables of turbine generator units are sometimes mounted elastically on their supports by means of springs, in order to minimize dynamic stresses in the ground, to avoid the transmission of vibration and noise to surrounding structures, and to avoid unwanted subsidence of the ground.
A third arrangement, disclosed in French Pat. No. 70 37372 combines the advantages of the previous two arrangements. It consists in supporting the condenser partially on the foundation slab using springs and partially on the table using mechanical linking means; as in the second arrangement, the connecting sleeve incorporates a flexible joint. This arrangement provides for decoupling the turbine from the condenser, so that it is not subject to the consequences of loads to which the condenser is subjected, while not subjecting the foundation slab to the atmospheric pressure loading when the condenser is evacuated.
This third arrangement has a disadvantage, and this applies also to the first arrangement, in that it does not provide for the exceptional loadings to which the condenser may be subject during testing. Specifically, prior to commissioning a "hydraulic test" is carried out to test the fluid tightness of the condenser tubes, by filling with water the space normally filled with steam. The resulting exceptional loading is not generally taken into account in designing the turbine skirt or condenser wall. It is therefore necessary to fit wedges or adjustable abutments under the condenser for the duration of the test. This involves the services of skilled maintenance personnel if major damage through mis-operation is to be avoided.
The objective of the present invention is to retain the advantages of the already known arrangements while reducing the risk of mis-operation and its consequences.